JP2018085361A - Resistance change element and memory device - Google Patents

Abstract

A variable resistance element and a memory device capable of stable operation are provided.
According to an embodiment, a resistance change element includes a first second conductive layer and a first layer. The first conductive layer includes at least one selected from the group consisting of silver, copper, zinc, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, tellurium, and bismuth. The second conductive layer includes at least one selected from the group consisting of platinum, gold, iridium, tungsten, palladium, rhodium, titanium nitride, and silicon. The first layer is provided between the first conductive layer and the second conductive layer, and includes oxygen and silicon. The first layer includes a plurality of holes smaller than the thickness of the first layer along the first direction from the second conductive layer toward the first conductive layer. The first layer does not contain carbon, or the composition ratio of carbon contained in the first layer to silicon contained in the first layer is less than 0.1.
[Selection] Figure 1

Description

  Embodiments described herein relate generally to a variable resistance element and a memory device.

  A memory device using a resistance change element has been proposed. In the variable resistance element, stable operation is desired.

Japanese Patent No. 5975121

  Embodiments of the present invention provide a variable resistance element and a memory device that can operate stably.

  According to the embodiment of the present invention, the variable resistance element includes a first conductive layer, a second conductive layer, and a first layer. The first conductive layer includes at least one selected from the group consisting of silver, copper, zinc, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, tellurium, and bismuth. The second conductive layer includes at least one selected from the group consisting of platinum, gold, iridium, tungsten, palladium, rhodium, titanium nitride, and silicon. The first layer is provided between the first conductive layer and the second conductive layer and includes oxygen and silicon. The first layer includes a plurality of holes smaller than the thickness of the first layer along a first direction from the second conductive layer toward the first conductive layer. The first layer does not contain carbon, or the composition ratio of carbon contained in the first layer to silicon contained in the first layer is less than 0.1.

FIG. 1 is a schematic cross-sectional view illustrating the variable resistance element according to the first embodiment. FIG. 2 is a graph illustrating characteristics of the resistance change element. FIG. 3 is a graph illustrating characteristics of the resistance change element. FIG. 4 is a graph illustrating characteristics of the resistance change element. FIG. 5 is a graph illustrating characteristics of the resistance change element. FIG. 6 is a schematic cross-sectional view illustrating the resistance change element according to the second embodiment.

Embodiments of the present invention will be described below with reference to the drawings.
The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between the parts, and the like are not necessarily the same as actual ones. Even in the case of representing the same part, the dimensions and ratios may be represented differently depending on the drawings.
In the present specification and drawings, the same elements as those described above with reference to the previous drawings are denoted by the same reference numerals, and detailed description thereof is omitted as appropriate.

(First embodiment)
FIG. 1 is a schematic cross-sectional view illustrating the variable resistance element according to the first embodiment.
As shown in FIG. 1, the variable resistance element 110 according to the first embodiment includes a first conductive layer 10, a second conductive layer 20, and a first layer 30.

  A first direction from the second conductive layer 20 toward the first conductive layer 10 is taken as a Z-axis direction. One direction perpendicular to the Z-axis direction is taken as an X-axis direction. A direction perpendicular to the Z-axis direction and the X-axis direction is taken as a Y-axis direction. The Z-axis direction is a stacking direction of the stacked body 15 including the first conductive layer 10, the second conductive layer 20, and the first layer 30.

  The first conductive layer 10 includes, for example, at least one selected from the group consisting of silver, copper, zinc, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, tellurium, and bismuth. The first conductive layer 10 includes, for example, at least one selected from the group consisting of silver and copper.

  The second conductive layer 20 includes, for example, at least one selected from the group consisting of platinum, gold, iridium, tungsten, palladium, rhodium, titanium nitride, and silicon.

  For example, the first conductive layer 10 is more easily ionized than the second conductive layer 20. The first conductive layer 10 functions as, for example, an ion source.

  The first layer 30 is provided between the first conductive layer 10 and the second conductive layer 20. The first layer 30 includes oxygen and silicon. In this example, the first layer 30 is in physical contact with, for example, the first conductive layer 10 and the second conductive layer 20.

  The first layer 30 includes a plurality of holes 35. The first layer 30 is porous. The plurality of holes 35 are smaller than the thickness t <b> 1 of the first layer 30. The thickness t1 is the length of the first layer 30 along the first direction (Z-axis direction). For example, the average size of the plurality of holes 35 is smaller than the thickness t1.

  The first layer 30 does not substantially contain carbon, for example. Alternatively, when the first layer 30 includes carbon, the composition ratio of carbon to silicon in the first layer 30 is less than 0.1. For example, the composition ratio of carbon contained in the first layer 30 to silicon contained in the first layer 30 is less than 0.1.

  By using such a first layer 30, for example, it has been found that good holding characteristics can be obtained as described later.

  The resistance change element 110 can be used as a memory cell of a memory device, for example.

  As illustrated in FIG. 1, the storage device 210 includes the resistance change element 110 and the control unit 70. The control unit 70 is electrically connected to the first conductive layer 10 and the second conductive layer 20. In this example, the first conductive layer 10 and the control unit 70 are electrically connected by the first wiring 71. The second conductive layer 20 and the control unit 70 are electrically connected by the second wiring 72. At least one of these wirings may be provided with a switching element such as a transistor.

  The control unit 70 can perform the first operation and the second operation. In the first operation, the control unit 70 makes the first potential of the first conductive layer 10 higher than the second potential of the second conductive layer 20. In the second operation, the control unit 70 makes the first potential of the first conductive layer 10 lower than the second potential of the second conductive layer 20. When the potential of the first conductor is higher than the potential of the second conductor, a current flows from the first conductor toward the second conductor.

  For example, in the memory device 210, the first electrical resistance between the first conductive layer 10 and the second conductive layer 20 after the first operation is equal to the first conductive layer 10 and the second conductive layer after the second operation. Lower than the second electrical resistance between 20.

  For example, metal element ions (for example, silver ions) contained in the first conductive layer 10 move toward the second conductive layer 20 by the first operation. This ion is considered to form a current path (for example, a filament) between the first conductive layer 10 and the second conductive layer 20. Thereby, after the first operation, the electrical resistance between the first conductive layer 10 and the second conductive layer 20 is low. The formed current path is maintained for a certain period of time after removing the potential difference. The first operation corresponds to, for example, a set operation. The voltage for forming the low resistance state is, for example, a set voltage.

  On the other hand, for example, due to the second operation, the formed current path becomes ions (for example, silver ions) and moves toward the first conductive layer 10. The current path disappears, for example. Thereby, the electrical resistance between the 1st conductive layer 10 and the 2nd conductive layer 20 becomes high after a 2nd operation | movement. The second electrical resistance after the second operation is higher than the first electrical resistance after the first operation. As described above, the resistance change occurs in the resistance change element 110. The second operation corresponds to, for example, a reset operation. The voltage for forming the high resistance state corresponds to, for example, a reset voltage.

  It is desirable that the resistance change as described above is stable even after the potential difference is removed. That is, it is desired that the resistance change element has good holding characteristics.

  In the resistance change element 110 and the memory device 210 according to the embodiment, it has been found that good holding characteristics can be obtained by using the first layer 30 as described above.

  Hereinafter, experimental results regarding the holding characteristics will be described.

In the first experiment, a titanium nitride film is provided as the second conductive layer 20 on the substrate. A plurality of types of silicon oxide films are formed thereon as the first layer 30 by plasma CVD (plasma-enhanced chemical vapor deposition: PE-CVD). In the experiment, two different types of gases are used as source gases. The first source gas is TEOS (Tetraethyl orthosilicate). In the film formation using the first source gas, conditions for forming a porous film (gas flow rate ratio, film formation temperature, etc.) are employed. The oxidizing gas used at the time of film formation is O ₂ gas. The second source gas is different from TEOS. It is known that a dense film is formed when the second source gas is used. These formed silicon oxide films are amorphous. A silver film is formed as a first conductive layer 10 on the silicon oxide film by sputtering.

  With respect to these samples, the density of the silicon oxide film is evaluated by X-ray reflectivity measurement (XRR: X-Ray Reflectivity). Then, the formation state of the plurality of holes 35 is evaluated by a scanning transmission electron microscope.

  Furthermore, the retention properties are evaluated for these samples. In the evaluation of the holding characteristics, a voltage (set voltage) corresponding to the first operation is applied to each of these samples, and the stacked body 15 is brought into a low resistance state. The electrical resistance immediately after these samples are produced is taken as the initial resistance. These samples are held at various “holding temperatures”. After being held at the “holding temperature”, the electrical resistance of the laminate 15 is measured. The elapsed time when the difference between the electrical resistance and the initial resistance is 0.2 times the initial resistance is defined as “holding time”.

FIG. 2 is a graph illustrating characteristics of the resistance change element.
FIG. 2 illustrates the evaluation result of “holding time”. The horizontal axis of FIG. 2 is the holding temperature parameter TP. The holding temperature parameter TP is 1000 times the reciprocal of the holding temperature (Kelvin). The smaller the holding temperature parameter TP, the higher the holding temperature. The vertical axis in FIG. 2 is the holding time RT. The holding time RT is a logarithmic display and is standardized. FIG. 2 shows the characteristics of the first sample SP01 using the first source gas and the characteristics of the second sample SP02 using the second source gas.

  As can be seen from FIG. 2, the holding time RT in the first sample SP01 is longer than the holding time RT in the second sample SP02. At the same holding temperature, the holding time RT in the first sample SP01 is 10 times or more than the holding time RT in the second sample SP02.

On the other hand, a plurality of holes 35 are observed in the first sample SP01. The density of the first sample SP01 is 2.0 g / cm ³ . 1 g / cm ³ is 1000 kg / m ³ .

On the other hand, the plurality of holes 35 are not formed in the second sample SP02, and the second sample SP02 is a dense film. The density of the second sample SP02 is 2.2 g / cm ³ . This high density is consistent with the fact that the plurality of holes 35 are not formed.

  As described above, it was found that good holding characteristics can be obtained by providing the plurality of holes 35 in the first layer 30.

  For example, in the first operation, a current path is formed by silver ions, and a low resistance state is formed. This current path is considered to be formed so as to connect a plurality of holes 35 in the silicon oxide film, for example. After this, if left unattended, silver in the current path tends to diffuse around. At this time, if a plurality of holes 35 are formed in the silicon oxide film, it is considered that silver tends to stay in the holes 35. It is presumed that this is a cause of a long holding time RT when a plurality of holes 35 are formed. On the other hand, when the hole 35 is not formed, since the diffusion of silver is not suppressed, it is considered that the formed current path is likely to disappear.

  The carbon contained in the first sample SP01 and the second sample SP02 is small. In these samples, the composition ratio C / Si (composition ratio of carbon to silicon) is 0.01 or less. The composition ratio C / Si is obtained by electron energy loss spectroscopy.

  As already described, in the embodiment, the first layer 30 is substantially free of carbon, for example. Alternatively, the composition ratio of carbon to silicon in the first layer 30 is less than 0.1. Due to the small amount of carbon contained in the first layer 30, for example, high stability can be obtained in the first layer 30.

  For example, when carbon is contained in the first layer 30, the characteristics of the first layer 30 are likely to change due to chemical changes (for example, oxidation of carbon). For example, when the first operation and the second operation are repeatedly performed in the resistance change element 110, the chemical change is accelerated. Further, for example, after the formation of the first layer 30, a heat treatment for the purpose of reducing the resistance of the wiring or the like may be performed. Such heat treatment accelerates the chemical change in the first layer 30. When carbon is contained in the first layer 30, the characteristics may be deteriorated by such heat treatment.

  In the embodiment, the first layer 30 is substantially free of carbon or low in carbon. Thereby, for example, a chemical change is suppressed and stable characteristics can be obtained.

  Thus, it becomes thermally stable by using the 1st layer 30 with few carbon and containing the several fine hole 35. FIG. Good retention characteristics are obtained. According to the embodiment, it is possible to provide a variable resistance element and a storage device that can perform stable operation.

  In the embodiment, for example, the plurality of holes 35 are smaller than the thickness t <b> 1 of the first layer 30. For example, the hole 35 does not penetrate the first layer 30. For example, if the size of the hole becomes excessively large, the hole penetrates the first layer 30. In this case, for example, the material included in the first conductive layer 10 or the material included in the second conductive layer 20 is easily filled in the holes. Leaks or shorts are likely to occur.

  In the embodiment, the plurality of holes 35 are sufficiently smaller than the thickness t 1 of the first layer 30. Thereby, a leak or a short circuit can be suppressed.

Furthermore, in the embodiment, the operating voltage can be reduced as described below.
In the second experiment, the first source gas is used, and the film formation conditions (gas flow ratio, film formation temperature, etc.) are changed. Thereby, various silicon oxide films are formed. Except for this, the sample is produced under the same conditions as in the first experiment. For these samples, the density of the silicon oxide film is measured. On the other hand, the operating voltage (set voltage) is measured for these samples.

FIG. 3 is a graph illustrating characteristics of the resistance change element.
The horizontal axis in FIG. 3 is the density Df (g / cm ³ ). The vertical axis represents the operating voltage Vs (set voltage). The operating voltage is standardized and displayed.

As shown in FIG. 3, the density of 1.85 g / cm ^{3 to} 2.13 g / cm ³ can be obtained by changing the film forming conditions using the first source gas. The difference in density corresponds to the formation state of the plurality of holes 35.

  As shown in FIG. 3, when the density Df is small, the operating voltage Vs is low.

  For example, as the density Df decreases, the size of the plurality of holes 35 increases. Alternatively, when the density Df decreases, the density of the plurality of holes 35 in the silicon oxide film increases. As the size or density of the holes 35 increases, a current path due to silver is likely to be formed. This is presumed to be a cause of a decrease in the operating voltage Vs when the density Df is small.

Hereinafter, a third experiment in which the relationship between the carbon concentration in the silicon oxide film and the operating voltage is examined will be described.
In the third experiment, the first source gas is used, and the film formation conditions (gas flow ratio, film formation temperature, etc.) are changed. The oxidizing gas used during film formation is O ₂ gas or N ₂ O gas. In general, when N ₂ O gas is used, carbon derived from organic substances in the first source gas (TEOS) tends to remain in the film. Under such conditions, various silicon oxide films are formed. Except for this, the sample is produced under the same conditions as in the first experiment. For these samples, the amount (density) of carbon in the silicon oxide film and the operating voltage (set voltage) are measured.

FIG. 4 is a graph illustrating characteristics of the resistance change element.
The horizontal axis in FIG. 4 is the composition ratio C / Si (composition ratio of carbon to silicon). The vertical axis represents the operating voltage Vs. The operating voltage is standardized and displayed.

In FIG. 4, a sample having a high composition ratio C / Si corresponds to the case where the oxidizing gas is N ₂ O gas. A sample having a low composition ratio C / Si corresponds to the case where the oxidizing gas is O ₂ gas. As shown in FIG. 4, when the composition ratio C / Si is lowered, the operating voltage Vs is lowered.

  When the composition ratio C / Si increases, it is considered that, for example, the plurality of holes 35 are easily filled with carbon. For this reason, it is considered that a current path is hardly formed. It is considered that when the composition ratio C / Si is low, a current path is easily formed, and as a result, the operating voltage Vs is reduced.

  In the embodiment, the composition ratio C / Si is, for example, 0.05 or less. The composition ratio C / Si may be 0.02 or less, for example. The composition ratio C / Si may be 0.015 or less, for example.

Hereinafter, the composition ratio of oxygen and silicon in the silicon oxide film will be described.
FIG. 5 is a graph illustrating characteristics of the resistance change element.
FIG. 5 shows the relationship between the composition ratio “O / Si” (composition ratio of oxygen to silicon) in the silicon oxide film and the density Df for a part of the sample of the third experiment. The horizontal axis in FIG. 5 is the composition ratio O / Si (composition ratio of oxygen to silicon). The vertical axis represents the density Df of the silicon oxide film.

As shown in FIG. 5, as the composition ratio O / Si decreases, the density Df increases. When the density Df is 2.2 g / cm ³ or more, the plurality of holes 35 are not substantially formed. A plurality of holes 35 are formed when the density Df is less than 2.2 g / cm ³ . For example, when the composition ratio O / Si exceeds 2.0, the plurality of holes 35 are stably formed. In the embodiment, the composition ratio O / Si (composition ratio of oxygen contained in the first layer 30 to silicon contained in the first layer 30) is higher than 2.2. In the embodiment, the composition ratio O / Si is, for example, 2.4 or less. As shown in FIG. 5, in the embodiment, the composition ratio O / Si may be, for example, more than 2.05 and 2.4 or less. A plurality of holes 35 can be obtained stably.

In the embodiment, the density of the first layer 30 is, for example, 1.5 g / cm ³ or more and less than 2.2 g / cm ³ . Density of the first layer 30 is, for example, less than 1.85 g / cm ³ or more 2.2 g / cm ^3. Density of the first layer 30 is, for example, less 1.85 g / cm ³ or more 2.0 g / cm ^3.

  In the embodiment, the average size of the plurality of holes 35 (the average length of the plurality of holes 35 along the first direction (Z-axis direction)) is 0 of the first layer 30 thickness t1 (see FIG. 1). .5 times or less. When the average size of the plurality of holes 35 is 0.5 times or less, it is possible to substantially suppress the plurality of holes 35 from continuing in the Z-axis direction in the first layer 30. Thereby, a short circuit or a leak can be suppressed. In the embodiment, the size of the plurality of holes 35 may be 0.2 times or less of the thickness t1. Short circuit or leak can be more stably suppressed.

  In the embodiment, for example, the average length of the plurality of holes 35 along the first direction is 0.6 nm or more and 1.5 nm or less. On the other hand, the thickness t1 of the first layer 30 is, for example, not less than 2 nanometers and not more than 10 nanometers.

  As already described, the second conductive layer 20 includes, for example, at least one selected from the group consisting of platinum, gold, iridium, tungsten, palladium, rhodium, titanium nitride, and silicon. This silicon contains impurities, for example. For example, the second conductive layer 20 includes at least one of polycrystalline silicon containing at least one element selected from the group consisting of boron, arsenic, and phosphorus, and amorphous silicon containing the above elements. For example, the resistivity of the second conductive layer 20 is 0.005 Ωcm or less, for example.

(Second Embodiment)
FIG. 6 is a schematic cross-sectional view illustrating the resistance change element according to the second embodiment.
As illustrated in FIG. 6, the variable resistance element 120 and the storage device 220 according to the second embodiment include a second layer 40 in addition to the first conductive layer 10, the second conductive layer 20, and the first layer 30. The first conductive layer 10, the second conductive layer 20, and the first layer 30 are the same as the resistance change element 110 or the memory device 210. Hereinafter, the second layer 40 will be described.

  The second layer 40 is provided between the first conductive layer 10 and the first layer 30. The relative dielectric constant of the second layer 40 is higher than the relative dielectric constant of the first layer 30.

  The second layer 40 is selected from, for example, an oxide containing at least one selected from the group consisting of aluminum, hafnium, titanium, tantalum, and zirconium, or a group consisting of aluminum, hafnium, titanium, tantalum, zirconium, and silicon. An oxynitride containing at least one of the above.

  By providing the second layer 40, for example, leakage current can be suppressed. The first layer 30 has a plurality of holes 35 as described above. For this reason, for example, when the second layer 40 is not provided, the first layer 30 may be damaged when the first conductive layer 10 is formed on the first layer 30. In such a case, a leak current is likely to occur. By providing the second layer 40 between the first layer 30 and the first conductive layer 10, for example, leakage current can be suppressed. For example, a stable switching operation can be obtained. For example, high retention characteristics can be obtained.

  Since the relative dielectric constant of the second layer 40 is higher than the relative dielectric constant of the first layer 30, for example, an increase in operating voltage due to the insertion of the second layer 40 can be suppressed as compared to when the relative dielectric constant is low.

  The thickness t2 of the second layer 40 (the length of the second layer 40 along the first direction) is, for example, not less than 2.0 nanometers and not more than 2 nanometers. When the thickness t2 of the second layer 40 is 0.2 nm or more, for example, intrusion of metal atoms in the formation of the first conductive layer 10 can be effectively suppressed. Thereby, leakage current can be effectively suppressed. When the thickness t2 of the second layer 40 is 2 nm or less, for example, the influence on the movement of metal ions can be suppressed. For example, a low operating voltage can be maintained.

  In the present embodiment, the second layer 40 can be formed by, for example, an atomic layer deposition (ALD) method. For example, the second layer 40 is formed on the first layer 30. The first conductive layer 10 is formed on the second layer 40.

  In the first and second embodiments, the second conductive layer 20 can be formed by, for example, a sputtering method or a vapor deposition method. The first layer 30 can be formed by, for example, a CVD method (including plasma CVD). The first conductive layer 10 can be formed by, for example, a sputtering method or a vapor deposition method.

  Information on the density of the first layer 30 is obtained by, for example, X-ray reflectivity measurement (XRR: X-Ray Reflectivity) or Rutherford Backscattering Analysis (RBS).

  Information regarding the composition of the first layer 30 includes, for example, electron energy loss spectroscopy (EELS), secondary ion mass spectrometry (SIMS), RBS, and X-ray photoelectron spectroscopy (XPS). : X-ray photoelectron spectroscopy).

  Information regarding the plurality of holes 35 in the first layer 30 is obtained by, for example, an electron microscope. For example, the information regarding the amount of the holes 35 and the size of the holes 35 can be obtained by, for example, the positron annihilation lifetime method or STEM.

  According to the embodiment, it is possible to provide a variable resistance element and a storage device that can perform stable operation.

  In this specification, the state of being electrically connected includes the state where two conductors are in direct contact. The state of being electrically connected includes a state in which two conductors are connected by another conductor (for example, a wiring or the like). The electrically connected state includes a state in which a switching element (a transistor or the like) is provided between the paths between the two conductors, and a state in which a current flows in the path between the two conductors can be formed.

  In the present specification, “vertical” and “parallel” include not only strict vertical and strict parallel, but also include variations in the manufacturing process, for example, and may be substantially vertical and substantially parallel. .

  The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. For example, regarding the specific configuration of each element such as the conductive layer, the layer, the wiring, and the control unit included in the variable resistance element and the memory device, the present invention is similarly implemented by appropriately selecting from a known range by those skilled in the art. As long as the same effect can be obtained, it is included in the scope of the present invention.

  Moreover, what combined any two or more elements of each specific example in the technically possible range is also included in the scope of the present invention as long as the gist of the present invention is included.

  In addition, all variable resistance elements and memory devices that can be implemented by those skilled in the art based on the variable resistance elements and memory devices described above as embodiments of the present invention also include the gist of the present invention. As long as it belongs to the scope of the present invention.

  In addition, in the category of the idea of the present invention, those skilled in the art can conceive of various changes and modifications, and it is understood that these changes and modifications also belong to the scope of the present invention. .

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 10 ... 1st conductive layer, 15 ... Laminated body, 20 ... 2nd conductive layer, 30 ... 1st layer, 35 ... Hole, 40 ... 2nd layer, 70 ... Control part, 71 ... 1st wiring, 72 ... 2nd Wiring, 110, 120 ... variable resistance element, 210, 220 ... storage device, C / Si ... composition ratio, Df ... density, O / Si ... composition ratio, RT ... holding time, SP01 ... first sample, SP02 ... second Sample, TP ... Holding temperature parameter, Vs ... Operating voltage, t1, t2 ... Thickness

Claims (11)

A first conductive layer comprising at least one selected from the group consisting of silver, copper, zinc, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, tellurium and bismuth;
A second conductive layer including at least one selected from the group consisting of platinum, gold, iridium, tungsten, palladium, rhodium, titanium nitride, and silicon;
A first layer including oxygen and silicon provided between the first conductive layer and the second conductive layer, wherein the first layer is a first direction from the second conductive layer toward the first conductive layer. A plurality of holes smaller than the thickness of the first layer along the first layer, the first layer does not contain carbon, or the composition ratio of carbon contained in the first layer to silicon contained in the first layer Wherein the first layer is less than 0.1;
A variable resistance element.   The resistance change element according to claim 1, wherein a composition ratio of oxygen contained in the first layer to silicon contained in the first layer is more than 2.0 and not more than 2.4.   3. The variable resistance element according to claim 1, wherein an average length of the plurality of holes along the first direction is 0.5 times or less of the thickness.   4. The resistance change element according to claim 1, wherein an average length of the plurality of holes along the first direction is 0.6 nm or more and 1.5 nm or less.   The resistance change element according to claim 1, wherein the thickness is not less than 2 nanometers and not more than 10 nanometers.   The second conductive layer includes at least one of polycrystalline silicon containing at least one element selected from the group consisting of boron, arsenic, and phosphorus, and amorphous silicon containing the element. The variable resistance element according to any one of the above. The resistance change element according to claim 1, wherein the density of the first layer is 1.5 g / cm ³ or more and less than 2.2 g / cm ³ .   The resistance change element according to claim 1, wherein the first conductive layer includes at least one selected from the group consisting of silver and copper. A second layer provided between the first conductive layer and the first layer;
9. The variable resistance element according to claim 1, wherein a relative dielectric constant of the second layer is higher than a relative dielectric constant of the first layer.   The second layer is selected from an oxide containing at least one selected from the group consisting of aluminum, hafnium, titanium, tantalum and zirconium, or selected from the group consisting of aluminum, hafnium, titanium, tantalum, zirconium and silicon. The resistance change element according to claim 7, comprising oxynitride including at least one. The resistance change element according to any one of claims 1 to 10,
A control unit electrically connected to the first conductive layer and the second conductive layer;
With
The controller is
A first operation in which a first potential of the first conductive layer is made higher than a second potential of the second conductive layer;
A second operation for making the first potential lower than the second potential;
Carried out
The first electrical resistance between the first conductive layer and the second conductive layer after the first operation is a second electrical resistance between the first conductive layer and the second conductive layer in the second operation. Storage device lower than electrical resistance.